1. Field of the Invention
Embodiments of the invention relate to a semiconductor device. More particularly, embodiments of the invention relate to a semiconductor integrated circuit device comprising a resistor.
This application claims priority to Korean Patent Application No. 1005-000776 filed Jan. 27, 2005, the subject matter of which is hereby incorporated by reference in its entirety.
2. Description of the Related Art
The integrated circuits formed in semiconductor devices are combinations of electrically connected active elements (e.g., transistors and diodes) and passive elements (e.g., resistors and capacitors). By designed combinations of these basic elements, innumerable integrated circuits may be formed having various outputs and/or performing various functions.
Resistors may be formed as part of a semiconductor integrated circuit from a doped polysilicon layer or from a region of a semiconductor substrate containing diffused impurities. As illustrated in FIG. 1, a device isolation layer 12 may be formed on a semiconductor substrate to thereby define an active region. A resistor then may be formed on device isolation layer 12 from a patterned polysilicon layer 16 having a predetermined length, thickness, and width. Alternatively, the resistor may be formed from an impurity diffusion layer 14 having a predetermined doping concentration, diffusion depth and width, within the active region. Electrodes 17a, 17b, 18a, and 18b may be connected to opposite ends of polysilicon pattern 16 and impurity diffusion layer 14, respectively. In this manner, resistors R1 and R2 may be variously formed between corresponding electrodes.
The output and/or functionality of a semiconductor integrated circuit must be carefully designed in view of the totality of factors influencing its performance. An accurate definition of the performance and tolerance of individual components forming the semiconductor integrated circuit is an important part of this design process. Unfortunately, resistors, such as those described above, constituting the semiconductor integrated circuit have well understood performance variations in relation to changing temperature. This variability may be expressed by a corresponding temperature coefficient. As a practical outcome of temperature related performance variations by resistor elements, a semiconductor integrated circuit may suffer from output signal variation or functional variance due to an increase or decrease in temperature.
For example, a semiconductor memory device may read data from a memory cell by comparing the output voltage of the memory cell with a reference voltage. A reference voltage generating circuit will often generate the reference voltage using a combination of transistors and resistors. Therefore a change in the internal resistance of this circuit as a function of temperature may cause a change in the reference voltage, which may generate an error in reading the data. Such reference voltages are also required for writing data to a memory cell.
More specifically, read, write and erase operations applied to a flash memory device are typically performed by applying a reference voltage to a memory cell. Thus variances in the performance characteristics of one or more resistors used to generate the reference voltage may cause variance in these fundamental flash memory operations, including failed read, write and erase operations.